Porous magnesia cement



I Z J ia' ,1 2o

a. COMPOSITIONS,

COATING on PLASTIC.

Patented July 3, 1934 UNITED STATES a f ,l, 965,538

PATENT OFFIC 1,965,538 POROUS MAGNESIA CEMENT ,5

Leroy 0. Stewart, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a

corporation of Michigan 1 No Drawing. Application April 27, 193,2,

Serial No. 607,895

12 Claims.

- other purposes.

Many proposals have been made for forming porous plastic cement mixtures by incorporating in the cement mix a material which is capable of giving off a gas to act as a leavening or pore- Iorming agent. For example, substances like baking powder have been proposed, which depend upon the reaction of an acid compound upon a carbonate to evolve carbon dioxide. Other suggestions include the use of a finely divided metal, like aluminum or zinc, to react with an alkaline constituent of the cement to generate hydrogen gas.

The aforementioned methods, however, are inapplicable for use with magnesia cements, which are composed of magnesia, a soluble magnesium salt and water as the principal active constituents. The magnesia present therein is sufficiently alkaline to neutralize the acid compoa gradually eyglved which form a nent of a baking powder type of gas generating v01 sor pores in he plastic mass.

agent, while it is not a strong enough alkali to react with a metal such as aluminum or zinc to produce hydrogen gas. The addition of a stronger alkali to the cement mixture for the lastmentioned purpose would have a deleterious effect upon the strength of the cement.

According to the present invention, a porous magnesia cement mixture is produced by incorporating in the wet cement mix a suitable amount of flnel divided ma esium or ma esium allo Such fiely divi ed metal has he property of reacting in the presence of water and the magnesium salt to generate hydrogen gas gradually. A control of the volume and rate of gas evolution may be obtained by varying the amount of metallic powder added, or the fineness thereof, or the particular alloy chosen for the purpose. The invention, then, consists of the improved porous cement compositions, together with the methods of preparing the same, hereinafter ,fully described and pointed out in the claims.

In carrying out my invention I prepare a wet mix of a magnesium oxychloride or oxysulphate cement, and incorporate therein a relatively small amount of finely divided magnesium or magnesium alloy. The metallic particles react slowlywith aqueous magnesium salt solution present in the mix to generate hydrogen gas. If The rate of gas generation, and hence the deno desired, however, the metallic ,particles may be added to the dry constituents previous to wetting, in which case no substantial gas evolution will occur until the cement mixture is mixed with water.

Any composition for a magnesium oxychloride or oxysulphate cement may be employed, such as are well known in the art. For example, for an oxychloride cement, a mixture of from 10 to 40 parts of calcined ma esite and from 90 to 60 parts of a' n m' ert filler, sucH as sand asbestos, sawdust etc., is gaged with a 18 to 22 e. so ution of ma nesium chloride until a wet mix' of suitaBle consis' tency for troweling or molding is prepared. In such mix is incorporated from about .95 to 2.0 per cent, based on weight of dry constituents, of

finely divided magesium or magnesium alloy. e mix ure is t en place in sui a e mo s, r applied with a trowel to a wall or the like as a stucco or plaster. This type of cement takes an initial set within from 1 to 8 hours, depending upon composition and atmospheric conditions. In the meantime, while still in a more or less plastic state, g as bubbles are p 01 y o In similar manner a porous product may be made from a magnesium oxysulphate cement containing magnesia, magnesium sulphate and water as active constituents, together with any suitable filler. In the case of the oxysulphate cements it may be advisable to add to the mix a small amount of a strengthener, such as a metallic phosphate or citrate, in accordance with the improvement disclosed in my prior Patents Nos.

1,853,521 and 1,853,522. To prepare the cement,

a dry mixture of magnesia and a suitable filler, such as sand, asbestos, etc., is made up in proportions of about 10 to 40 parts of magnesia to from 90 to 60 parts of filler, and the whole gaged to a proper consistency with a magnesium sulphate solution -"of 22 to 32 B. strength. It a strengthener is used, it may conveniently be dissolved in the magnesium sulphate solution, in proportion of 0.5 to 3 per cent of the sulphate content thereof figured as MgSO4.7H2O. The finely divided magnesium or magnesium alloy is incorporated in the wet mix in amount of .05 to 2.0 per cent of the solids therein. The action of the sulphate on the metal-particles is somewhat slower than in the case of the chloride, but the eiiect is the same in producing a porous mass due to the generation of hydrogen gas therein.

gree of porosity of the product, may be controlled centage of magnesium to another metal proby varying the amount and fineness of the metalduces an alloy which is much more susceptible to lie particles, and also the composition of the chemical action th'a'ii'feither of the constituent alloy used. Special effects may be secured by a metals. This is especially true in the case of 5 partial or incomplete mixing of the metal paralloys of magnesium with copper, nickel and ticle into the plastic mass, thereby forming bands, lead Reactive alloys of magnesium wi ese streaks or layers of porous material interspersed metals may be prepared in which the magnesium within the whole mass. Considerable latitude content varies from as high as 99 per cent to as is permissible in the amount of metallic parlow as 10 per cent, or even less. Over the greater 10 ticles added. About 1 to 2 per cent, based on part of this range the alloys are characteristically 85 the weight of dry solids, is sufficient to produce brittle, hence adapted for reducing to a comabout the maximum porosity, according to which minuted condition according to the usual methods. the volume of the hardened material may be in- These alloys are chemically more reactive than creased by as much as to per cent over ispure magnesium. In alloys of ma nesium with 15 that of a similar cement to which no metallic aluminum and zinc the tendency to brittleness particles have been added. On the other hand, 1's still presenm to a lesser degree, and a I have prepared special artist's stone to resemble higher percentage of the alloying metal is re- Travertine marble in which as low as .05 per cent quired to produce a typically brittle alloy. Such of finely divided magnesium was added and mixed last-mentioned alloys are in general less reactive 20 into certain portions only of the mass. Anexcess than pure magnesium. It is apparent, thereof metallic particles over the maximum amount fore, that the general class of magnesium alloys stated above, however, is not harmful to the propcontaining a substantial proportion of magneerties of the hardened cement, since the presence sium, e.g. upwards of 10 per cent thereof, when of free metallic particles in the hardened mass in finely divided form, may be utilized in 25 does not cause injury due to crumbling or dismy invention, which is understood to include the integration thereof. addition to a plastic magnesia cement of finely If a still greater increase in porosity is desired, divided particles of magnesium or of any magthis may be accomplished by adding an emulsinesium alloy containing a substantial proportion fying agent along with the metallic particles. of magnesium. Preferably, the alloys suitable 30 Such emulsifying agent acts as a gas-'entraining for the purpose are'th'oseof magnesium with any agent to hinder or retard the escape of the gas o n e or more of the metals a ummum, copper, tin,

bubbles formed within the plastic mass, and zinc nickel or lead. causes a greater swelling of the same. In thisme'mlments of my invention, the way the volume of the porous mass may be infollowing illustrative examples are given, which, 3 creased to as much as twice that of the cement however, are not to be construed as limiting in no f' itself without the addition of the metallic parany way the scope of the invention.

ticles and emulsifier. As examples of such emul- Exam 1 sifying agents glue, soaps emulsified asphalt Fo- 3 tation oils, anm 1 e, may e men ione e To make a Eg porous building block, a dry 40 mntity of the agent is immaterial to the mix was prepared consisting of 40 parts by weight principle of the invention, inasmuch as any of the of plastic magnesia, 58 parts of granulated wood known materials may be employed, as desired. charcoal and 2 parts of asbestos, to which was Another means of further increasing the poadded 0.5 to 1.0 per cent of finely divided magrosity of the hardened mass is to incorporate nesium. The mass was then gaged with a 22 B. 45 in the plastic cement mix an agent capable of magnesium chloride solution to a proper consistretarding the setting of the cement, such as ency for molding. The increase in volume of the bO a Zine S111 hate e11 r0115 e er in set and hardened block formed therefrom was a 50 11 7 Sa L Zine; E we about 43 per cent as compared with the same mix bal e e cemen mix so rea y e to which no metallic particles were added.

mg more slowly, is enabled to swell to a greater E amp 2 extent due to the continued generation of gas r therein for a longer time. If desired, both a A dry mix was 'prepared consisting of 40 parts retard r n m s yin agent m y be eInof magnesia, 58 parts of granulated charcoal and P y ogether. 2 parts of asbestos, with which was incorporated 55 Considerable variation in the rate and amount 6 parts of emulsified asphalt and 1 part of finely of as ev luti n may be effected y yin th divided magnesium. It was then gaged with a size of the metallic particles. The smaller the 22 B. magnesium chloride solution to a molding Particles, the more rapid is the evolution of as. consistency. The block formed therefrom after In n r h i y V ry fr m about 10 to setting showed an increase in volume of 95 per 60 100 mesh according to the standard screen scale. t over th t bt i d ith th same ix from There is a W de range of alloy Compositions which the metallic particles and emulsifier were which are suitable for the purposes of the initt i vention. In fact, substantially any alloy containing about 5 to 10 per cent of magnesium or Example 3 65 mo e y be used, although in general alleys A dry mix the same as that in Example 2 was containing upwards of 50 P ent magnesium prepared, and gaged to a molding consistency W111 be preferred. Ma e is known to alloy with a 24 B. magnesium sulphate solution. The readily with most E'tfie com Tnon metals except increase in volume of the hardened block was 55 iron; specifically it alloys in all proportions with per cent as compared with the check sample. 7 aluminum, coEper zinc tinE lead antimony, nickel an many 0 er metals. n most cases sue a Z6 4 loys are characterized by an eutectic type of struc- A dry mix was prepared the same as in Example ture which tends to cause brittleness, and hence 2, except that 1 part of a finely divided alloy conaids in mechanically comminuting the metal. taining 65 per cent magnesium and 35 per cent 75 In some cases the addition of only a small peraluminum was used as the metallic ingredient.

The mass was gaged with a 22 B. magnesium chloride solution to a molding consistency. The increase in volume of the hardened block was 47 per cent.

To a dry mix consisting of 25 parts of magnesia, 65 parts of marble flour and 10 parts of powdered talc were added varying amounts of finely divided magnesium, as shown in the table, and the whole was gaged with a 22 B. magnesium chloride solution to a medium thin consistency. The tabulated results show the increase in volume of the hardened porous mass as compared with one to which no magnesium particles were added. In the table the percentage of magnesium is based upon the weight of the dry mix.

Amount Size of par- Increase in added ticles volume Percent Mesh Percent The same dry mix as in Example 5 was used, with which was incorporated 0.5 per cent of 48- mesh particles of an alloy containing 65 per cent magnesium and 35 per cent aluminum, the whole being gaged to a medium consistency with a 22 B. magnesium chloride solution. The increase in volume of the porous mass was 30 per cent.

Example 7 The dry mix of Example 5 was mixed with 0.5 per cent of 48-mesh particles of magnesium, and the mass gaged with a 28 B. solution of magnesium sulphate containing 0.5 per cent of citric acid, based on its sulphate content figured as MgSO4.'7H2O. The increase in volume of the porous mass was 50 per cent.

'of Example 5 was used, with which was incorporated 0.5 per cent of 48-mesh particles of magnesium, 0.4 per cent of an emulsified oil and 3.0 per cent of borax, and the whole was gaged with a 22 Be. magnesium chloride solution. The increase in volume of the hardened porous mass was per cent.

As already pointed out, other magnesium alloys in finely divided form, as well as other emulsifying agents or retarders, may be employed without departing from the scope and principle of the invention. Likewise the proportions of ingredients in the dry mix, and the type of filler, may be varied in accordance with the known state of the art. Concisely stated, therefore, the invention comprises a plastic magnesia cement, whether an oxychloride or oxysulphate cement, with which is incorporated a relatively small amount of finely divided magnesium or magnesium alloy, either with or without the further addition of an emulsifying agent or of a retarder or both.

This application is a continuation-in-part of my prior application, Serial No. 257,105, filed February 25, 1928.

In the claims, the term magnesium is understood to include magnesium alloys, by which is meant any alloys of magnesium with other metexamine:

als, containing a substantial percentage of magnesium.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invention:-

1. The method of making porous magnesia cement mixtures of the class consisting of magnesium oxychloride and magnesium oxysulphate cements which comprises adding a relatively small amount of finely divided magnesium to the plastic cement mass.

2. The method of making porous magnesia cement mixtures of the class consisting of magnesium oxychloride and magnesium oxysulphate cements which comprises adding a relatively small amount of finely divided magnesium and a gas-entraining agent to the plastic cement mass.

3. The method ,of making porous magnesia cement mixtures of the class consisting of magnesium oxychloride and magnesium oxysulphate cements which comprises adding a relatively small amount of finely divided magnesium, a gas-entraining agent and a retarder to the plastic cement mass.

'4. The method of making porous magnesia cement mixtures of the class consisting of magnesium oxychloride and magnesium oxysulphate cements which comprises incorporating in the plastic cement mass from .05 to 2.0 per cent, based on the weight of dry constituents, of particles of magnesium having a fineness of from 10 to 100 mesh.

5. The method of making porous magnesia cement mixtures of the class consisting of magnesium oxychloride and magnesium oxysulphate cements which comprises incorporating in the plastic cement mass a gas-entraining agent and from .05 to 2.0 per cent, based on the weight of dry constituents, of particles of magnesium having a fineness of from 10 to 100 mesh.

6. The method of making porous magnesia cement mixtures of the class consisting of magnesium oxychloride and magnesium oxysulphate cements which comprises incorporating in the plastic cement mass a gas-entraining agent, a retarder and from .05 to 2.0 per cent, based on the weight of dry constituents, of particles of magnesium having a fineness of from 10 to 100 mesh.

7. A cementitious mixture comprising a plastic magnesia cement mass of the class consisting of magnesium oxychloride and magnesium oxysulphate cements to which has been added a relatively small amount of finely divided magneslum.

8. A cementitious mixture comprising a plastic magnesia cement mass of the class consisting of magnesium oxychloride and magnesium oxysulphate cements to which has been added a relatively small amount of finely divided magnesium and a gas-entraining agent.

9. A cementitious mixture comprising a plastic magnesia cement mass of the class consisting of magnesium oxychloride and magnesium oxysulphate cements to which has been added a relatively small amount of finely divided magnesium, a gas-entraining agent and a retarder.

finely divided magnesium and a gas-entraining agent.

12. A cementitious mixture comprising magnesia, a. soluble magnesium salt of the class consisting of magnesium chloride and magnesium sulphate, water, a relatively small amount of finely divided magnesium, a gas-entraining agent and a retarder.

LEROY C. STEWART. 

